Hidden parts of the feed tabs and the megamenu are left out instead of hidden

A feed tab's name and the megamenu's toggle are now only rendered where they show, rather than rendered and then hidden
by a class, so nothing runs or ships for a part no one sees. The validator hint and the phone menu keep their hiding
class on purpose: the browser reveals the first, and the second is also the desktop sidebar. The house-rules checks move
to 1.1.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W4YtEJrgxG12Pc39Fai8Bd

CLAUDE.md

@@ -867,6 +867,10 @@ ones with an HR id as errors in every build and in Rider, here and in `PrivaPub.
 | Components | `[Inject]` in `@code`, never `@inject` (HR0101) |
 | Components | Disable controls with `IsDefaultDisabled` (plus local conditions), never bare offline state (HR0104) |
 | Components | Every text/number input declares `autocomplete`, except credentials (HR0103, HR0105) |
+| Components | Hide by not rendering (HR0107): what a user, role or state should not see is left out with `@if`, never hidden by a class or style a condition switches on. A static responsive class (`hidden max-md:inline`) is fine. Two files keep a hiding class on purpose (`HouseRulesHiddenToggleAllowed`): `DValidatorHint` (daisyUI's `validator-hint hidden` collapses the hint while its field is valid and the browser shows it on `:user-invalid`, so the node must exist) and `NavMenu` (the same panel is the sidebar from md and the phone menu below it, so it stays rendered and only its phone visibility follows `isMenuOpen`) |
+| Components | No MudBlazor here, so the picker rules (HR0108, HR0320) don't apply; a list of records to pick from still searches rather than listing everything |
+| Services | A server failure's message starts with its code (`[ERR0030006] …`, HR0013 on the server); show it as it comes and never match on it — branch on `ErrorCode` (`FailureCodes`) or the status |
+| All | No spreadsheet import or export unless asked for (HR0319) |
 | Services | A failure the client builds itself is a 400 that names its kind in `ErrorCode` (`FailureCodes`), never a 5XX; only a server's own 5XX passes through (HR0007) |
 | Services | `Task<WebResult>` for mutations, `Task<List<T>>` (`[]` on error) for lists, `Task<T>` with a default for values |
 | Localization | Every user-facing string through `Localizer`, its key in **both** `AllStrings.resx` and `AllStrings.it.resx` |